When containers are to be filled with liquid gas it is essential that filling be stopped at an appropriately early stage so that the liquid gas occupies only part of the container space, usually about 80% of its total volume. Failing this, there is a considerable risk that the cylinder will explode, if it is subjected to heating, even if only to a relatively moderate degree.
For this purpose it is customary to perform the filling process through a channel with a valve connected to a float so as to be closed when the liquid in the cylinder has reached the prescribed, highest level. It is, however, conditional to the closing of the valve at the correct stage that the gas cylinder is in an upright position during filling, since a slanting position can cause the float to react too early or too late. From the point of view of safety, too early closing of the valve cannot, of course, cause any damage, whereas if the valve closes at too late a stage the result may be dangerous overfilling. A customer or consumer would normally not be aware of this risk, but he would, on the other hand, soon discover that if the cylinder is tilted or held at an angle in a certain direction it is possible to fill an extra amount of gas into the cylinder, and the customer will naturally be tempted to take advantage of this possibility, especially if payment is fixed for "a charge", regardless of the amount filled.
The risk of overfilling can be obviated when filling takes place at an authorized filling station, as special safety devices can be installed to prevent all filling, unless the cylinder is fixed in the correct filling position, but for one thing such safety devices can--intentionally or unintentionally--be put out of action, and for another gas filling often takes place in completely unsupervised conditions, e.g. from a large gas tank installed on customer's premises.
A purpose of the invention is to provide a valve device which in all circumstances may prevent overfilling of liquid gas cylinders, but it should be noticed that the basic principles of this valve device may also be utilized in other connections where it is required to interrupt a fluid flow, e.g. the flow of powder or granular material into a portable container, after the level of the amount filled into the container has reached a pre-stipulated height.